Note that where possible, the Si5351A’s Clk0 and Clk1 outputs are operated in quadrature with a
90-degree phase offset. The relationship does not hold at frequencies below 3.2MHz and may not
hold into VHF (To Be Determined).
4.17
CAT Control commands (PC remote operation)
The CAT command system is intended to allow the QCX+ to be used with logging software
(general and contest) which uses CAT control commands to query the transceiver for information
entered into the log, typically operating frequency, mode etc. A subset of the Kenwood TS-480
command set is implemented, with a few minor modifications.
Hardware description:
All microcontroller pins are already in use. The microcontroller serial port peripheral is already
used by the LCD_D4 and LCD_D5 signals. Therefore sharing is necessary. Two resistors R49 and
R50, together with one diode D6, allow this sharing. In the QCX+ and QCX-mini models, these
components are already installed and there is a 3.5mm jack for the CAT serial port. In the QCX
later PCB revisions, the components are installed and there are PCB pads for a 3-pin header.
Earlier QCX PCB revisions would require you to modify them by adding the three components.
Remember QCX+ RxD connects to the computer TxD,
and the QCX+ TxD connects to the computer RxD;
there is a swap as shown. Most PCs do not have
actual serial ports anymore and the typical set-up will
be to use a USB to Serial converter.
Be sure to use
one with TTL level serial data, NOT RS232 which is
a different (higher) voltage.
These three signals are routed to a 3.5mm stereo jack connector at the rear panel of the QCX+
and QCX-mini models, with the following connection scheme:
Tip:
QCX+ RxD
Ring:
QCX+ TxD
Sleeve:
Ground
The microcontroller only writes to the serial port or the LCD, in atomic operations; it does not
attempt to write to the LCD while serial port write is in progress, nor write to the serial port while an
LCD write is in progress. To prevent conflicts, LCD_D4 (processor’s RxD signal) is driven by the
external serial device TxD signal via 1K resistor R49. This prevents two circuits trying to drive
each other, if an LCD-write and serial port write occur at the same time. The processor TxD signal
is shared with LCD_D5. When writing to the LCD, this signal pulses and would be interpreted by
the remote serial device as some spurious characters. To prevent this, a 270-ohm series resistor
is used, and a diode to IC2 Pin 25 (which is also the DVM analog measurement channel). During
QCX operating manual, firmware 1.07, manual edit 0.03
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